Troubleshooting method and apparatus

ABSTRACT

A troubleshooting method and a troubleshooting apparatus are disclosed. The troubleshooting method includes: sending a forward detection message to at least one node on a path to be detected, where the forward detection message carries information about a forward path to be detected and information about a backward path to be detected; and detecting faults according to a backward detection message returned by the at least one node. With the troubleshooting method and the troubleshooting apparatus disclosed herein, troubleshooting operations such as fault detection and fault location can be performed for the forward path and the backward path that require bidirectional path detection.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2010/070818, filed on Mar. 2, 2010, which claims priority toChinese Patent Application No. 200910008095.0, filed on Mar. 2, 2009,both of which are hereby incorporated by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates to the field of communicationtechnologies, and in particular, to a troubleshooting method and atroubleshooting apparatus.

BACKGROUND OF THE INVENTION

With the rapid development of information technologies, people requiremore and more bidirectional interactive services such as Internetaccess, Video on Demand (VOD), videoconference, videophone,telemedicine, and tele-education. Operators have an urgent need ofcarrying out such network Value Added Services (VASs) to increase thenetwork operation revenue.

A bidirectional interactive service requires two paths: a forward pathfor carrying outbound traffic, and a backward path for carrying inboundtraffic, to implement the interaction. The traffic in the two directionsmay be carried over one bidirectional Label Switched Path (LSP) or twospecified unidirectional LSPs in two opposite directions, or by othermeans. A key to ensuring Quality of Service (QoS) of a bidirectionalinteractive service and deploying the bidirectional interactive servicemassively is to detect, locate and handle faults in a simple andefficient way.

In the process of implementing the present invention, the inventor findsthat: for a bidirectional interactive service, a fault in one directionmay affect or even lead to termination of the service in the otherdirection, and therefore, the troubleshooting needs to be performed inboth directions simultaneously. In other circumstances that involvedetection of faults in two directions, it is also necessary to detect,locate and handle the faults in the forward path and the backward pathsimultaneously, and a technology for detecting and handling the faultsin two directions is also required. Besides, a bidirectionaltroubleshooting tool, which is capable of detecting the forward path andthe backward path simultaneously, is required due to the emergence ofbidirectional LSPs to detect two directions of a bidirectional LSPsimultaneously. A bidirectional LSP may include a forward LSP and abackward LSP that have the same route and the same LSP Identifier (ID),or may include a forward unidirectional LSP and a backwardunidirectional LSP that have different LSP IDs and may have differentnodes and different links except that the first nodes of the two LSPsare the same.

However, the troubleshooting tools in the prior art such as LSP Ping andLSP Trace generally support only the unidirectional handling mode. Ifthe fault detection is required on the forward path and the backwardpath respectively, it is necessary to operate the troubleshooting toolon both sides respectively, and detect, locate and handle the faults onboth sides independently, and it is necessary to transmit connectivityfault information and switching information between both sides in timeto implement protection switching in both directions simultaneously.This handling mode increases the signaling and processing overhead,network load, complexity of operation and maintenance, and the operationcost, and can hardly meet the troubleshooting requirements ofbidirectional interactive services.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a troubleshooting methodand a troubleshooting apparatus for solving the technical problems suchas fault detection, fault location and fault handling for abidirectional path that requires bidirectional path detection, and theproblems cannot be solved with troubleshooting tools in the prior art.

Such objectives are fulfilled through the following technical solution:

A troubleshooting method includes: sending a forward detection messageto at least one node on a path to be detected, where the forwarddetection message carries information about a forward path to bedetected and information about a backward path to be detected; anddetecting faults according to a backward detection message returned bythe at least one node.

A troubleshooting apparatus includes: a forward detection messagesending unit, configured to send a forward detection message to at leastone node on a path to be detected, where the forward detection messagecarries information about a forward path to be detected and informationabout a backward path to be detected; and a fault detecting unit,configured to detect faults according to a backward detection messagereturned by the at least one node.

A troubleshooting method includes: receiving a forward detection messagesent by a detection initiation node on a path to be detected, where theforward detection message carries information about a forward path to bedetected and information about a backward path to be detected; andassembling a backward detection message according to the forwarddetection message, and sending the backward detection message to thedetection initiation node.

A troubleshooting apparatus includes: a forward detection messagereceiving unit, configured to receive a forward detection message sentby a detection initiation node on a path to be detected, where theforward detection message carries information about a forward path to bedetected and information about a backward path to be detected; abackward detection message assembling unit, configured to assemble abackward detection message according to the forward detection message;and a backward detection message sending unit, configured to send thebackward detection message to the detection initiation node.

With the troubleshooting method and the troubleshooting apparatusdisclosed herein, troubleshooting operations such as fault detection andfault location can be performed for the forward path and the backwardpath that require bidirectional path detection.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings listed below are intended to help further understand thepresent invention, and constitute part of this application, but shallnot be construed as a limitation on the present invention.

FIG. 1 is a method flowchart according to an embodiment of the presentinvention;

FIG. 2 is a schematic diagram of interaction according to an embodimentof the present invention;

FIG. 3 is a schematic diagram of interaction according to anotherembodiment of the present invention;

FIG. 4 is a schematic diagram of interaction according to anotherembodiment of the present invention;

FIG. 5 is a block diagram of an apparatus according to an embodiment ofthe present invention;

FIG. 6 is a method flowchart according to another embodiment of thepresent invention; and

FIG. 7 is a block diagram of an apparatus according to anotherembodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

To make the objectives, technical solution, and advantages of thepresent invention clearer, the following describes the embodiments ofthe present invention in detail with reference to accompanying drawings.The exemplary embodiments of the present invention and the descriptionof the embodiments are illustrative in nature, and shall not beconstrued as limitations on the present invention.

An embodiment of the present invention provides a troubleshootingmethod, and is detailed below with reference to an accompanying drawing.

FIG. 1 is a method flowchart according to an embodiment of the presentinvention. As shown in FIG. 1, the troubleshooting method in thisembodiment includes the following steps:

101. A detection initiation node sends a forward detection message to atleast one node on a path to be detected, where the forward detectionmessage carries information about a forward path to be detected andinformation about a backward path to be detected.

This embodiment is applicable to a unidirectional detection scenario, inwhich the path to be detected has only one direction and no backwardpath. In this scenario, the forward detection message may carry onlyinformation about the forward path to be detected. The information aboutthe forward path to be detected includes destination node, path traveledby the message, and/or message forwarding mode. Therefore, the node thatreceives the forward detection message can verify consistency of pathinformation and assemble the backward detection message according to theinformation about the forward path to be detected.

This embodiment is further applicable to the bidirectional detectionscenario, in which the path to be detected has a forward direction and abackward direction. In this scenario, the forward detection message notonly carries information about the forward path to be detected, but alsocarries information about the backward path to be detected. Theinformation about the backward path to be detected specifies thebackward path for the backward detection message. For example, theinformation about the backward path to be detected specifies that themode of returning the backward detection message is to return themessage along the backward path corresponding to forward path to bedetected (in the case that the forward path to be detected has abackward path). In this way, the backward path is specified.Alternatively, a backward path ID, such as Forwarding Equivalence Class(FEC) ID, an LSP ID, a Tunnel ID, may be used to specify the path forreturning the backward detection message. The ID of the path shall notbe construed as a limitation on this embodiment. Another mode is: Thepath for returning the backward detection message is specified bybackward path constraint information. In this case, the node thatreceives the forward detection message further needs to match the pathaccording to the backward path specified in the forward detectionmessage so as to select the path for returning the backward detectionmessage.

102. The detection initiation node detects faults according to thebackward detection message returned by the at least one node.

In the case of unidirectional detection, because the information aboutthe forward path to be detected in the forward detection messagespecifies the path to be traveled by the forward detection message inthis embodiment, the node that receives the forward detection messageverifies consistency of the forward path to be detected between the dataplane and the control plane according to the information about theforward path to be detected, and returns a backward detection message orreturns no backward detection message. Therefore, upon receiving thebackward detection message, the detection initiation node detects faultsaccording to the content of the backward detection message; if nobackward detection message is received, the detection initiation nodeconsiders that the path to be detected is faulty.

In the case of bidirectional detection, because the information aboutthe forward path to be detected in the forward detection messagespecifies the path to be traveled by the forward detection message inthis embodiment, and the information about the backward path to bedetected in the forward detection message specifies the path to betraveled by the backward detection message, the node that receives theforward detection message verifies consistency of the forward path to bedetected between a data plane and a control plane according to theinformation about the forward path to be detected in the forwarddetection message, matches the path according to the information aboutthe backward path to be detected in the forward detection message, andreturns a backward detection message along a specified path and/or anon-specified path or returns no backward detection message. Therefore,upon receiving the backward detection message, the detection initiationnode detects faults according to the state and content of the receivedbackward detection message (which is detailed in other embodimentsherein); if no backward detection message is received, the detectioninitiation node determines whether the path to be detected is faultyaccording to original settings.

In this embodiment, the path to be traveled by the forward detectionmessage and the path to be traveled by the backward detection messageare specified, so that the forward path and the backward path can bedetected simultaneously.

A troubleshooting method is provided in another embodiment of thepresent invention, and is detailed below with reference to anaccompanying drawing.

FIG. 2 is a schematic diagram of interaction for detecting networkconnectivity by applying the method disclosed herein. In FIG. 2, R1 is adetection initiation node; R2 and R3 are intermediate nodes; and R4 is adestination node. In this embodiment, the forward route (link and nodes)of the path to be detected may be the same as or different from thebackward route. As shown in FIG. 2, the troubleshooting method in thisembodiment includes the following steps:

201. R1 sends a forward detection message such as a request message. Theforward detection message arrives at the destination node R4 after beingforwarded by the intermediate nodes R2 and R3.

In this embodiment, in the case of unidirectional detection, the forwarddetection message carries only information about the forward path to bedetected such as destination node, path traveled by the message, ormessage forwarding mode, so that the destination node R4 can verifyconsistency of the path between a data plane and a control planeaccording to such information, and then return the backward detectionmessage such as a reply message along a random path, which is notfurther detailed here.

In this embodiment, in the case of bidirectional detection, the forwarddetection message not only carries the information about the forwardpath to be detected, but also carries the information about the backwardpath to be detected. The mode of returning the backward detectionmessage can be specified by the information about the backward path tobe detected, for example, returning the message along a specified path,returning the message along a random path, or returning the messagealong a specified path and a random path simultaneously. The specifiedpath here may be a backward path corresponding to the forward path to bedetected, or may be a definitely specified backward path, or may beconstraint information of a specified backward path, for example,explicit path or other constraint conditions. To achieve that purpose,the forward detection message carries an ID of the specified path forreturning the backward detection message.

In the information about the backward path to be detected, one or morebackward paths may be specified. In this way, the backward detectionmessage can be returned along multiple specified paths, so that multiplebackward paths can be detected simultaneously.

The ID of the path to be traveled specified in the information about theforward path to be detected and the information about the backward pathto be detected may be denoted by an FEC ID (Forwarding EquivalenceClass), an LSP ID (Label Switch Path identification), and/or a tunnelTunnel ID (Tunnel identification), or may be constraint information ofthe backward path, for example, explicit path. The ID of the path shallnot be construed as a limitation on this embodiment.

202. R4 receives the forward detection message, verifies consistency ofthe forward path to be detected between the data plane and the controlplane, and assembles and processes a backward detection messageaccording to the mode of returning the backward detection message, wherethe returning mode is specified in the forward detection message.

The verification of consistency of the forward path to be detectedbetween the data plane and the control plane is to verify consistency ofthe path to be detected between the data plane and the control plane,namely, to verify whether R4 is the destination node in the forward pathin the information about the forward path to be detected, where theinformation about the forward path to be detected is carried in theforward detection message. If R4 is the destination node, the path isconsistent; otherwise, the path is not consistent.

If the mode of returning the backward detection message, which isspecified in the information about the backward path to be detected, inthe forward detection message is to return the message along a specifiedpath, R4 assembles the backward detection message and addsidentification information of the backward path to the backwarddetection message. For example, the identification information of thebackward path is FEC information. Further, R4 matches the backward pathaccording to the identification information of the backward pathspecified in the information about the backward path to be detected,namely, checks whether R4 has a backward path specified in the forwarddetection message. If the matching succeeds, R4 sends a backwarddetection message to R1 along a specified backward path; if the matchingfails, R4 sends a backward detection message that carries return codeinformation to R1 along a random path.

The identification information of the backward path, namely, theinformation about the specified backward path to be detected, carried inthe backward detection message may be copied from the forward detectionmessage, or may be added according to the information about thespecified backward path to be detected in the forward detection message.The mode of obtaining the identification information of the backwardpath is not limited in this embodiment.

If the mode of returning the backward detection message specified in theforward detection message is to return the message along a specifiedpath and a non-specified path simultaneously, R4 assembles the backwarddetection message and matches the backward path in the same way asmentioned above. If the matching succeeds, R4 sends a backward detectionmessage to R1 along a specified path and a random path; if the matchingfails, R4 sends a backward detection message that carries return codeinformation to R1 along a random path.

The return code information may be fault type information such as “thespecified path does not exist” or “the specified path mismatches”, ormay be notification information such as “the specified path matchessuccessfully”.

The specified path for returning the backward detection message may beidentified by adding a Type Length Value (TLV) of the specified path, orby setting the corresponding identification field or otheridentification information. The identification information of thespecified path may be an FEC ID or an LSP ID, and/or a Tunnel ID, or maybe constraint information of the backward path, for example, explicitpath.

203. R1 receives the backward detection message returned by R4, anddetermines link connectivity according to the state of receiving theforward detection message and the backward detection message.

After receiving the backward detection message, R1 first determines thepath for receiving the backward detection message. If the receiving pathis the backward path specified in the forward detection message, namely,if the backward detection message is returned to R1 along the specifiedbackward path, R1 verifies consistency of the backward path to bedetected between the data plane and the control plane. If the backwardpath to be detected is consistent, the bidirectional link is free fromconnectivity faults; if the backward path is not consistent or thereceiving path is not the backward path specified in the forwarddetection message, namely, if the backward detection message is notreturned along the specified backward path, R1 performs furthertroubleshooting according to the return code information in the backwarddetection message or notifies the network management system.

If the receiving path is the backward path specified in the forwarddetection message and a non-specified path, namely, if the backwarddetection message is returned to R1 along the specified path and thenon-specified path simultaneously, R1 also needs to verify consistencyof the backward path to be detected between the data plane and thecontrol plane for the backward detection message returned along thespecified path, and the verification method is not further detailedhere.

If the receiving path is a non-specified path, namely, if the backwarddetection message is returned to R1 along a non-specified path only, R1determines whether the path to be detected is faulty according to thereturn code information in the backward detection message received alongother paths.

If R1 receives no backward detection message, the forward path to bedetected is probably faulty. In this case, the faulty node may belocated by other means, for example, by means of unidirectional ping inthe prior art or bidirectional trace in other embodiments of the presentinvention. The bidirectional trace in other embodiments of the presentinvention is described later.

In this embodiment, the intermediate nodes R2 and R3 only normallyforward but do not handle the forward detection message sent by R1 orthe backward detection message sent by R4.

In this embodiment, a path is specified for the backward detectionmessage, and therefore, the forward path and the backward path aredetected simultaneously, and the troubleshooting method can be executedon only one side to detect faults and verify connectivity in bothdirections simultaneously.

A troubleshooting method is provided in another embodiment of thepresent invention, and is detailed below with reference to anaccompanying drawing.

FIG. 3 is a schematic diagram of interaction for verifying networkconnectivity by applying the method disclosed herein. In FIG. 3, R1 is adetection initiation node; R2 and R3 are intermediate nodes; and R4 is adestination node. In this embodiment, the forward route (link and nodes)of the path to be detected may be the same as the backward route. Asshown in FIG. 3, the troubleshooting method in this embodiment includesthe following steps:

301. R1 sends a forward detection message to R2.

The forward detection message could further includes a Collecting PathInformation (CPI) indication such as CPI TLV besides the contentdescribed in the second embodiment so as to notify the intermediatenodes to collect the information about the path to be detected andreturn the information to the first node. The collected path informationmay include: node ID, distance (count of hops) to the first node, labelallocated to the previous hop, and previous-hop node ID.

R1 may send the forward detection message to R2 by setting Time To Live(TTL) to 1.

302. R2 receives the forward detection message, verifies consistency ofthe forward path to be detected between the data plane and the controlplane, and assembles and processes a backward detection message.

After receiving the forward detection message, R2 handles the message inthe same way as R4 handling the received forward detection message inthe second embodiment above, for example, verifies consistency of thepath to be detected, assembles the backward detection message, andmatches the backward path. Because the forward detection message carriesindication information which instructs the intermediate nodes to collectpath information, the intermediate node R2 collects path informationwhen assembling the backward detection message, and adds the collectedpath information to the backward detection message. Afterward, R2 sendsthe backward detection message to R1 along the path specified in theforward detection message, or along the specified path and anon-specified path, or along a non-specified path simultaneously, whichhas been described in step 202 in the second embodiment above and is notfurther detailed here.

The verification of consistency of the path to be detected is to alsoverify consistency of the forward path to be detected between the dataplane and the control plane, namely, to verify whether R2 is theintermediate node or destination node in the forward path to be detectedin the information about the forward path to be detected, where theinformation about the forward path to be detected is carried in theforward detection message.

303. R1 receives the backward detection message returned by R2, anddetermines link connectivity according to the state of receiving theforward detection message and the backward detection message.

This process is the same as step 203 in the second embodiment above, andis not further detailed here.

If R1 receives no backward detection message returned by R2, thebidirectional link or node between R1 and R2 is regarded as faulty.

304. R1 sends a forward detection message to R3.

This step is the same as step 301 above, which is not further detailedhere.

R1 may send the forward detection message to R3 by setting TTL to 2.

305. R3 receives the forward detection message, and assembles andhandles a backward detection message.

This step is the same as step 302 above, which is not further detailedhere.

306. R1 receives the backward detection message returned by R3, anddetermines link connectivity according to the state of receiving theforward detection message and the backward detection message.

This step is the same as step 303 above, which is not further detailedhere.

If R1 receives no backward detection message returned by R3, thebidirectional link or node between R2 and R3 is regarded as faulty.

307. R1 sends a forward detection message to R4.

This step is the same as step 301 above, which is not further detailedhere.

R1 may send the forward detection message to R4 by setting TTL to 3.

308. R4 receives the forward detection message, and assembles andhandles a backward detection message.

This step is the same as step 302 above, which is not further detailedhere.

309. R1 receives the backward detection message returned by R4, anddetermines link connectivity according to the state of receiving theforward detection message and the backward detection message.

This step is the same as step 303 above, which is not further detailedhere.

If R1 receives no backward detection message returned by R4, thebidirectional link or node between R3 and R4 is regarded as faulty.

In this embodiment, the TTL is set, and the detection initiation node R1sends a forward detection message to intermediate nodes R2 and R3 andthe destination node R4. For example, R1 sends a forward detectionmessage with TTL=1 to R2, and R2 handles the forward detection message,collects path information, records the information into a backwarddetection message, and returns the backward detection message to thefirst node R1 along a backward path specified in the forward detectionmessage; afterward, R1 sends a forward detection message with TTL=2 toR3, and R3 handles and assembles the backward detection message in asimilar way, and returns the backward detection message to the firstnode; this process goes on until the message arrives at the destinationnode R4. By specifying a path for the backward detection message in theforward detection message, the technical solution in this embodimentdetects the forward path and the backward path simultaneously, collectsthe path information at the same time, and detects the paths in bothdirections simultaneously and verifies connectivity by executing thetroubleshooting method on only one side. The signaling overhead isreduced, and the implementation is simplified.

A troubleshooting method is provided in an embodiment of the presentinvention, and is detailed below with reference to an accompanyingdrawing.

FIG. 4 is a schematic diagram of interaction for verifying networkconnectivity by applying the method disclosed herein. In FIG. 4, R1 is adetection initiation node, R2 and R3 are intermediate nodes, and R4 is adestination node. In this embodiment, the forward route (link and nodes)of the path to be detected may be the same as the backward route. Asshown in FIG. 4, the troubleshooting method in this embodiment includesthe following steps:

401. R1 sends a forward detection message to R2 by setting TTL to 1.

402. R1 receives a backward detection message returned by R2.

403. R2 keeps TTL=1 for the forward detection message, adds a labeldirected to R3, and sends the message to R3.

404. R1 receives a backward detection message returned by R3.

405. R3 keeps TTL=1 for the forward detection message, adds a labeldirected to R4, and sends the message to R4.

406. R1 receives the backward detection message returned by R4.

The steps of this embodiment are similar to the steps of the thirdembodiment. In the third embodiment, the first node R1 sends the forwarddetection message to the intermediate nodes R2 and R3 and thedestination node R4 directly by setting TTL to 1, 2 and 3. In the fourthembodiment, the first node R1 sends the forward detection message to thenext-hop node R2 by setting TTL to 1, and R2 returns a backwarddetection message; R2 goes on to send the forward detection message tothe next-hop node by setting TTL to 1 until the message arrives at thedestination node R4.

The processing mode of the nodes in the steps of the fourth embodimentis the same as the processing mode in the third embodiment, which is notfurther detailed here.

In this embodiment, the TTL is set to 1 when the first node R1 sends aforward detection message; the TTL expires when the forward detectionmessage arrives at R2, and R2 handles the message, collects pathinformation, and returns the path information in a backward detectionmessage to the first node R1. Meanwhile, R2 sets TTL to 1 for theforward detection message, adds a label directed to R3, and sends themessage to R3. The forward detection message arriving at R3 is handledin the same way, and finally arrives at the destination node R4. Aftercollecting the path information, R4 returns the path information in abackward detection message to the first node. If a path is specified forthe backward detection message, the backward detection message isreturned along the specified path, or along the specified path or anon-specified path simultaneously according to the setting. Byspecifying a path for the backward detection message in the forwarddetection message, the technical solution in this embodiment detects theforward path and the backward path simultaneously, collects the pathinformation at the same time, and detects the paths and verifiesconnectivity in both directions simultaneously by executing thetroubleshooting method on only one side. The signaling overhead isreduced, and the implementation is simplified.

A troubleshooting apparatus is provided in another embodiment of thepresent invention, and is detailed below with reference to anaccompanying drawing.

FIG. 5 is a block diagram of an apparatus according to an embodiment ofthe present invention. As shown in FIG. 5, the troubleshooting apparatusin this embodiment includes:

a forward detection message sending unit 51, configured to send aforward detection message to at least one node on a path to be detected,where the forward detection message carries information about a forwardpath to be detected and information about a backward path to bedetected; and

a fault handling unit 52, configured to handle faults according to thebackward detection message returned by the at least one node.

If at least one node is the destination node of the path to be detected,the forward detection message is forwarded to the destination node bythe intermediate nodes of the path to be detected, and the faulthandling unit 52 is configured to detect faults according to thebackward detection message returned by the destination node.

If at least one node is the intermediate node and at least one node isthe destination node of the path to be detected, the forward detectionmessage is sent to the intermediate node and the destination noderespectively, and the fault handling unit 52 is configured to detect andlocate faults according to the backward detection message returned bythe intermediate node and the destination node.

If at least one node is the intermediate node and at least one node isthe destination node of the path to be detected, the forward detectionmessage, the TTL of which is set to 1, is forwarded through the next-hopnode, and the forwarding goes on until the message arrives at thedestination node; and the fault handling unit 52 is configured to detectand locate faults according to the backward detection message returnedby the intermediate node and the destination node.

The fault handling unit 52 includes a receiving path determining module521, a path consistency verifying module 522, and a fault handlingmodule 523.

The receiving path determining module 521 is configured to determinewhether the backward detection message is returned along the specifiedbackward path by comparing the backward path specified in the forwarddetection message for returning the backward detection message with thepath in which the backward detection message has been received.

The path consistency verifying module 522 is configured to verifyconsistency of the backward path to be detected between a data plane anda control plane if the backward detection message is returned along thespecified backward path.

The fault handling module 523 is configured to determine whether thepath to be detected is faulty according to the verification result ofthe path consistency verifying module 522 or the determining result ofthe receiving path determining module 521.

If the verification result of the path consistency verifying module 522is that the backward path to be detected is consistent between the dataplane and the control plane, the fault handling module 523 checkswhether the backward path to be detected is connected.

If the verification result of the path consistency verifying module 522is that the backward path to be detected is not consistent between thedata plane and the control plane, the fault handling module 523 proceedsaccording to the return code information in the backward detectionmessage.

If the determining result of the receiving path determining module 521is that the backward detection message is not returned along thespecified backward path, but along other paths, the fault handlingmodule 523 proceeds according to the return code information in thebackward detection message returned by at least one node along the otherpath.

If the determining result of the receiving path determining module 521is that the backward detection message is returned along the specifiedbackward path and other paths simultaneously, the fault handling module523 checks whether the path to be detected is connected according to thebackward detection message received on the specified backward path.

The forward detection message may further carry an indication ofcollecting path information. The indication instructs at least one nodeto collect information about the path to be detected, and return theinformation through a backward detection message.

The troubleshooting apparatus in this embodiment specifies a path forthe backward detection message in the forward detection message, andtherefore, the forward path and the backward path are detectedsimultaneously, and the path information is collected at the same time.Moreover, the troubleshooting method can be executed on only one side todetect faults and verify connectivity in both directions simultaneously.

A troubleshooting method is provided in another embodiment of thepresent invention, and is detailed below with reference to anaccompanying drawing.

FIG. 6 is a method flowchart according to an embodiment of the presentinvention. As shown in FIG. 6, the troubleshooting method in thisembodiment includes the following steps:

601. Receive a forward detection message sent by a detection initiationnode on a path to be detected, where the forward detection messagecarries information about a forward path to be detected and informationabout a backward path to be detected.

602. Verify consistency of the forward path to be detected between adata plane and a control plane according to the forward detectionmessage, assemble a backward detection message, and send the backwarddetection message to the detection initiation node.

If the forward detection message only carries information about theforward path to be detected, it is only necessary to verify consistencyof the forward path to be detected, and the verification result servesas a basis for deciding whether to return a backward detection messageto the detection initiation node. If it is decided to return thebackward detection message to the detection initiation node, the messagemay be returned along a random path. In this way, the detectioninitiation node can check whether the link is connected according to theinformation in the backward detection message. For details, see thefirst embodiment to the fifth embodiment above.

The backward detection message may be assembled in the following way:

If the current node has the backward path to be detected specified inthe information about the backward path to be detected in the forwarddetection message, the current node adds the path information about thebackward path such as FEC information to a backward detection messageaccording to the indication of collecting path information in theforward detection message, and sends the backward detection message tothe detection initiation node along the specified backward path to bedetected or along the specified backward path to be detected and otherpaths simultaneously.

If the current node does not have the backward path to be detectedspecified in the information about the backward path to be detected inthe forward detection message, the current node adds return codeinformation to a backward detection message, and sends the backwarddetection message to the detection initiation node along other paths.

If the current node is not the destination node of the path to bedetected, but an intermediate node, the method in this embodimentfurther includes:

603. Set the TTL of the forward detection message to 1, and send theforward detection message to the next-hop node, whereupon the message isforwarded by next hops consecutively until the message arrives at thedestination node, so that the next-hop node and the destination node canassemble the backward detection message according to the forwarddetection message and send the backward detection message to thedetection initiation node.

The troubleshooting method in this embodiment is applicable when thedetection initiation node detects connectivity of the link to bedetected. For example, in the second embodiment, R4 may apply the methodin this embodiment to interact with the detection initiation node R1 todetect connectivity of the link to be detected. The troubleshootingmethod in this embodiment is also applicable when the detectioninitiation node verifies connectivity of the link to be detected. Forexample, in the third embodiment and the fourth embodiment, R2, R3, andR4 may apply the method in this embodiment to interact with thedetection initiation node R1 to verify connectivity of the link to bedetected. For details, see the second embodiment to the fourthembodiment above.

The troubleshooting method in this embodiment assembles a backwarddetection message according to the forward detection message, andchooses whether to return a backward detection message according to thebackward path specified in the forward detection message. In this way,the forward path and the backward path are detected simultaneously, andthe path information is collected at the same time. Moreover, thetroubleshooting method can detect faults and verify connectivity in bothdirections simultaneously and just needs to be executed on only oneside.

A troubleshooting apparatus is provided in an embodiment of the presentinvention, and is detailed below with reference to an accompanyingdrawing.

FIG. 7 is a block diagram of an apparatus according to an embodiment ofthe present invention. As shown in FIG. 7, a troubleshooting apparatusin this embodiment includes:

a forward detection message receiving unit 71, configured to receive aforward detection message sent by a detection initiation node on a pathto be detected, where the forward detection message carries informationabout a forward path to be detected and information about a backwardpath to be detected;

a backward detection message assembling unit 72, configured to assemblea backward detection message according to the forward detection message;and

a backward detection message sending unit 73, configured to send thebackward detection message to the detection initiation node.

According to this embodiment, the backward detection message assemblingunit 72 includes: a path consistency verifying module 721, a pathmatching module 722, and a backward detection message assembling module723.

The path consistency verifying module 721 is configured to verifywhether the forward path to be detected is consistent between a dataplane and a control plane.

The path matching module 722 is configured to match the backward path tobe detected specified in the information about the backward path to bedetected in the forward detection message.

The backward detection message assembling module 723 is configured toassemble the backward detection message according to the verificationresult of the path consistency verifying module 721 and the matchingresult of the path matching module 722.

The backward detection message assembling unit 72 is configured to addFEC information to a backward detection message if the current node hasthe backward path to be detected specified in the information about thebackward path to be detected in the forward detection message; and thebackward detection message sending unit 73 sends the backward detectionmessage to the detection initiation node along the specified backwardpath to be detected, or along the specified backward path to be detectedand other paths simultaneously.

The backward detection message assembling unit 72 is further configuredto add return code information to a backward detection message if thecurrent node does not have the backward path to be detected specified inthe information about the backward path to be detected in the forwarddetection message; and the backward detection message sending unit 73sends the backward detection message to the detection initiation nodealong other paths.

The backward detection message assembling unit 72 is further configuredto collect information about the path to be detected if the forwarddetection message carries an indication information of collecting pathinformation, and add the collected path information to the backwarddetection message.

According to this embodiment, the troubleshooting apparatus may furtherinclude:

a forward detection message sending unit 74, configured to set the TTLof the forward detection message to 1, and send the forward detectionmessage to the next-hop node, whereupon the message is forwarded bynext-hop nodes consecutively until the message arrives at thedestination node, so that the next-hop node and the destination node canassemble the backward detection message according to the forwarddetection message and send the backward detection message to thedetection initiation node.

The troubleshooting apparatus in this embodiment assembles a backwarddetection message according to the forward detection message, andchooses whether to return a backward detection message according to thebackward path specified in the forward detection message. In this way,the forward path and the backward path are detected simultaneously, andthe path information is collected at the same time. Moreover, thetroubleshooting method can detect faults and verify connectivity in bothdirections simultaneously and just needs to be executed on only oneside.

The method or steps described herein may be implemented through hardwaredirectly or through a software module of a processor, or through both ofthem. The software module may be located in a Random Access Memory(RAM), a computer memory, a Read Only Memory (ROM), an ElectricallyProgrammable Read Only Memory (EPROM), an Electrically ErasableProgrammable Read Only Memory (EEPROM), a register, a hard disk, aremovable disk, a Compact Disk-Read Only Memory (CD-ROM), or any otherstorage media well-known in the art.

The objectives, technical solution, and benefits of the embodiments ofthe present invention are detailed above. Although the invention hasbeen described through some exemplary embodiments, the invention is notlimited to such embodiments. All modifications, equivalent replacements,and improvements made by those skilled in the art without departing fromthe spirit and principle of the invention shall fall within the scope ofthe invention.

What is claimed is:
 1. A troubleshooting method performed by a detectioninitiation node for detecting a fault in a bidirectional Label SwitchedPath (LSP), comprising: sending, by a detection initiation node, aforward detection message to at least one node on a bidirectional LSP tobe detected, the bidirectional LSP to be detected comprising a forwardpath to be detected and a backward path to be detected, wherein theforward detection message carries information about the forward path tobe detected and information about the backward path to be detected, theinformation about the backward path to be detected includes ForwardingEquivalence Class (FEC), Label Switched Path Identifier (LSP ID) orTunnel Identifier (Tunnel ID), which is used to specify the backwardpath to be detected; receiving, by the detection initiation node, abackward detection message returned by the at least one node in responseto the forward detection message; and performing, by the detectioninitiation node, a fault detection on the bidirectional LSP to bedetected according to the backward detection message based ondetermining whether the backward detection message is returned throughthe specified backward path to be detected.
 2. The method according toclaim 1, wherein: the at least one node is a destination node of theforward path to be detected, the forward detection message is forwardedto the destination node by an intermediate node on the forward path tobe detected, and the fault detection is performed according to thebackward detection message returned by the destination node.
 3. Themethod according to claim 1, wherein: the forward detection message issent to an intermediate node and a destination node on the forward pathto be detected respectively, and the fault detection and faultpositioning is performed according to the backward detection messagesreturned by the intermediate node and the destination node respectively.4. The method according to claim 1, wherein: the forward detectionmessage whose Time To Live (TTL) is set to 1 is sent to a next-hop nodethrough an intermediate node until the forward detection message arrivesat a destination node, wherein the intermediate node and the destinationnode are on the forward path to be detected, and the fault detection andfault positioning is performed according to the backward detectionmessages returned by the intermediate node and the destination noderespectively.
 5. The method according to claim 3, wherein: the forwarddetection message further carries an indication of collecting pathinformation, and the indication instructs the at least one node tocollect information about the bidirectional LSP to be detected, andreturn the information about the bidirectional LSP to be detectedthrough the backward detection message.
 6. The method according to claim1, wherein: the step of performing the fault detection according to thebackward detection message returned by the at least one node comprises:checking whether the bidirectional LSP to be detected is connectedaccording to the backward detection message if the backward detectionmessage returned by the at least one node is received on the backwardpath specified in the information about the backward path to bedetected.
 7. The method according to claim 1, wherein: the step ofperforming the fault detection according to the backward detectionmessage returned by the at least one node comprises: processingaccording to return code information in the backward detection messagereturned by the at least one node along other path if the backwarddetection message returned by the at least one node is received on theother path.
 8. The method according to claim 1, wherein: the step ofperforming the fault detection according to the backward detectionmessage returned by the at least one node comprises: checking whetherthe bidirectional LSP to be detected is connected according to thebackward detection message received on the backward path to be detectedif the backward detection message returned by the at least one node isreceived on the backward path specified in the information about thebackward path to be detected and other path.
 9. The method according toclaim 6, wherein: the step of checking whether the bidirectional LSP tobe detected is connected according to the backward detection messagecomprises: checking whether the backward path to be detected isconsistent between a data plane and a control plane according to thebackward detection message; if the backward path is consistent betweenthe data plane and the control plane, determining that the bidirectionalLSP to be detected is connected; if the backward path is not consistentbetween the data plane and the control plane, processing according toreturn code information in the backward detection message.
 10. Atroubleshooting apparatus for detecting a fault in a bidirectional LabelSwitched Path (LSP), comprising: a forward detection message sendingunit, configured to send a forward detection message to at least onenode on a bidirectional LSP to be detected, the bidirectional LSP to bedetected comprising a forward path to be detected and a backward path tobe detected, wherein the forward detection message carries informationabout the forward path to be detected and information about the backwardpath to be detected, wherein the information about the backward path tobe detected includes Forwarding Equivalence Class (FEC), Label SwitchedPath Identifier (LSP ID) or Tunnel Identifier (Tunnel ID), which is usedto specify the backward path to be detected; and a fault handling unit,configured to receive a backward detection message returned by the atleast one node in response to the forward detection message, and performa fault detection on the bidirectional LSP to be detected according tothe backward detection message based on determining whether the backwarddetection message is returned through the specified backward path to bedetected.
 11. A troubleshooting method performed by a node on abidirectional Label Switched Path (LSP) for detecting a fault in thebidirectional LSP, comprising: receiving a forward detection messagesent by a detection initiation node on a bidirectional LSP to bedetected, the bidirectional LSP to be detected comprising a forward pathto be detected and a backward path to be detected, wherein the forwarddetection message carries information about the forward path to bedetected and information about the backward path to be detected, whereinthe information about the backward path to be detected includesForwarding Equivalence Class (FEC), Label Switched Path Identifier (LSPID) or Tunnel Identifier (Tunnel ID), which is used to specify thebackward path to be detected; and assembling a backward detectionmessage according to the forward detection message; and in response tothe forward detection message, sending the backward detection message tothe detection initiation node.
 12. The method according to claim 11,wherein: the step of assembling the backward detection message accordingto the forward detection message comprises: checking whether the forwardpath to be detected is consistent between a data plane and a controlplane according to the forward detection message, and matching thebackward path if the forward path is consistent between the data planeand the control plane.
 13. The method according to claim 12, wherein thematching of the backward path comprises: if a current node has thebackward path specified in the information about the backward path to bedetected, adding the information about the backward path to the backwarddetection message, and sending the backward detection message to thedetection initiation node along the specified backward path, or alongthe specified backward path and other path simultaneously.
 14. Themethod according to claim 12, wherein the matching of the backward pathcomprises: if a current node does not have the backward path specifiedin the information about the backward path to be detected, adding returncode information to the backward detection message, and sending thebackward detection message to the detection initiation node along otherpath.
 15. The method according to claim 14, wherein: the step ofassembling the backward detection message according to the forwarddetection message further comprises: if the forward detection messagecarries an indication of collecting path information, collectinginformation about the bidirectional LSP to be detected according to theindication and adding the collected path information to the backwarddetection message.
 16. A troubleshooting apparatus for detecting a faultin a bidirectional Label Switched Path (LSP), comprising: a forwarddetection message receiving unit, configured to receive a forwarddetection message sent by a detection initiation node on a bidirectionalLSP to be detected, the bidirectional LSP to be detected comprising aforward path to be detected and a backward path to be detected, whereinthe forward detection message carries information about the forward pathto be detected and information about the backward path to be detected,wherein the information about the backward path to be detected includesForwarding Equivalence Class (FEC), Label Switched Path Identifier (LSPID) or Tunnel Identifier (Tunnel ID), which is used to specify thebackward path to be detected; a backward detection message assemblingunit, configured to assemble a backward detection message according tothe forward detection message; and a backward detection message sendingunit, configured to send, in response to the forward detection message,the backward detection message to the detection initiation node.